docs: def handle_unset_statement_group(self, line: str, position: int, tokens: ParseResults) -> ParseResults:
          """Unset the statement group, or raises an exception if it is not set.
  
          :raises: MissingAnnotationKeyWarning
          """
          if self.statement_group is None:
              raise MissingAnnotationKeyWarning(self.get_line_number(), line, position, BEL_KEYWORD_STATEMENT_GROUP)
          self.statement_group = None
          return tokens